Exporter/Stackdriver: Fix k8s_container resource. (#1889)

Author: songy23

exporters/stats/stackdriver/src/main/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtils.java

@@ -683,7 +683,6 @@ private static Map<String, String> getK8sResourceLabelsMappings() {
     Map<String, String> resourceLabels = new LinkedHashMap<String, String>();
     resourceLabels.put("project_id", STACKDRIVER_PROJECT_ID_KEY);
     resourceLabels.put("location", CloudResource.ZONE_KEY);
-    resourceLabels.put("instance_id", HostResource.ID_KEY);
     resourceLabels.put("cluster_name", K8sResource.CLUSTER_NAME_KEY);
     resourceLabels.put("namespace_name", K8sResource.NAMESPACE_NAME_KEY);
     resourceLabels.put("pod_name", K8sResource.POD_NAME_KEY);

exporters/stats/stackdriver/src/test/java/io/opencensus/exporter/stats/stackdriver/StackdriverExportUtilsTest.java

@@ -844,7 +844,6 @@ public void setResourceForBuilder_K8sInstanceType() {
     Map<String, String> expectedResourceLabels = new HashMap<String, String>();
     expectedResourceLabels.put("project_id", "proj1");
     expectedResourceLabels.put("location", "zone1");
-    expectedResourceLabels.put("instance_id", "instance1");
     expectedResourceLabels.put("cluster_name", "cluster1");
     expectedResourceLabels.put("namespace_name", "namespace1");
     expectedResourceLabels.put("pod_name", "pod1");
@@ -856,7 +855,7 @@ public void setResourceForBuilder_K8sInstanceType() {
     assertThat(monitoredResourceBuilder.getType()).isNotNull();
     assertThat(monitoredResourceBuilder.getLabelsMap()).isNotEmpty();
     assertThat(monitoredResourceBuilder.getType()).isEqualTo("k8s_container");
-    assertThat(monitoredResourceBuilder.getLabelsMap().size()).isEqualTo(7);
+    assertThat(monitoredResourceBuilder.getLabelsMap().size()).isEqualTo(6);
     assertThat(monitoredResourceBuilder.getLabelsMap())
         .containsExactlyEntriesIn(expectedResourceLabels);
   }